Add Discord bot (moderation, filters, scheduling, roles, invites, site integration)

Standalone bot/ service (its own package.json/Dockerfile) managed entirely
through a new admin-only Discord Bot panel — token stored encrypted in the
DB and pushed to the bot process in-memory, never an env var. Built in
phases, each independently verified against a live Discord guild:

- Bot skeleton: gateway connection, internal shared-secret API, self-heals
  on its own restart by pulling config from the site
- Moderation core: /ban /kick /mute /warn /warnings + mod-log channel
- Word/invite/spam filtering with leetspeak-resistant normalization and a
  staff role/channel allowlist
- Scheduled messages: recurring (cron) and one-off channel posts
- Role assignment: button role menus, auto-role on join, temp roles,
  bulk role ops
- Auto-rotating primary invite with an audit log
- Site integration: news-publish -> Discord announce webhook, manual
  /announce, read-only /wiki search

Also fixes a pre-existing bug in both DB pools (server + bot): the mariadb
driver defaulted to timezone 'local', silently mis-serializing bound Date
params by the host's local offset instead of the DB's UTC session.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

bot/src/invites/inviteRotator.js

@@ -0,0 +1,37 @@
+// Shared by both /invite rotate and the weekly cron job (inviteScheduler.js)
+// so manual and automatic rotations log identically. maxAge is set to match
+// the rotation cadence as defense-in-depth: if the scheduled rotation were
+// ever to silently stop running, the invite still expires on its own instead
+// of staying live forever.
+const guildConfig = require('../model/guildConfig')
+const inviteLog = require('../model/inviteLog')
+const createLogger = require('../utils/logger')
+
+const log = createLogger('invites')
+
+const ROTATION_MAX_AGE_SECONDS = 7 * 24 * 60 * 60 // 7 days
+
+async function rotate(client, guildId, { triggeredBy, triggeredByTag } = {}) {
+  const channelId = await guildConfig.getInviteChannelId(guildId)
+  if (!channelId) throw new Error('No invite channel configured — set one with /invite channel first.')
+
+  const channel = await client.channels.fetch(channelId)
+  if (!channel || !channel.isTextBased()) throw new Error('Configured invite channel is missing or not text-based.')
+
+  const current = await inviteLog.getCurrent(guildId)
+  if (current) {
+    try {
+      await channel.guild.invites.delete(current.invite_code, 'Invite rotation')
+    } catch (err) {
+      log.warn('failed to revoke previous invite (may already be gone)', { message: err.message })
+    }
+    await inviteLog.markRevoked(current.id)
+  }
+
+  const invite = await channel.createInvite({ maxAge: ROTATION_MAX_AGE_SECONDS, unique: true, reason: 'Invite rotation' })
+  await inviteLog.record({ guildId, channelId, inviteCode: invite.code, triggeredBy, triggeredByTag })
+  log.info('invite rotated', { code: invite.code, triggeredBy: triggeredByTag || 'automatic (scheduled)' })
+  return invite
+}
+
+module.exports = { rotate }

bot/src/invites/inviteScheduler.js

@@ -0,0 +1,31 @@
+// Weekly automatic invite rotation (Sundays at midnight). A missing invite
+// channel config just skips quietly (warn-logged) — most guilds won't set
+// this up on day one, and that shouldn't spam errors every week until they do.
+const cron = require('node-cron')
+
+const inviteRotator = require('./inviteRotator')
+const createLogger = require('../utils/logger')
+
+const log = createLogger('invites')
+
+let task = null
+
+function start(client, guildId) {
+  task = cron.schedule('0 0 * * 0', async () => {
+    try {
+      await inviteRotator.rotate(client, guildId, {})
+    } catch (err) {
+      log.warn('scheduled invite rotation skipped', { message: err.message })
+    }
+  })
+  log.info('invite rotation scheduler started')
+}
+
+function stop() {
+  if (task) {
+    task.stop()
+    task = null
+  }
+}
+
+module.exports = { start, stop }